Proximity Sensors

marcusbaxy · Jan 30, 2016

Hi,

I have been presented with 2 x Sick proximity sensors at a clients site to detect product entering/exiting a machine to varify line running etc. I was expecting this to be a 24vdc input to my panel which I have PLC input provision for. Unfortunately I cannot quote a part number for the sensor.

I am trying to work with the sensors but am not having any success yet. I assume the sensors are PNP as they have been purchased in UK and that appears to be the norm. When I supply the device with 24vdc the green lamp illuminates and when I place a body for it to detect infront there is a yellow lamp that illuminates on and off when blocked. The sensor has a pre made 5 wire M12 connector (like a Brad Harrison cable) connected to a terminal box to extend the cable back to my panel. I can measure the 24vdc supply and measure 24vdc on the "switch" when the sensor is dectecting a body. As soon as I connect that "switch" to the terminal in my panel for the input the previously measured 24vdc drops to 5.7vdc so this is insufficient to drive my input. There is a 2nd sensor that wires straight back to the panel with out the terminal box and that behaves in the same manner.

Is the wiring incorrect or do I have the wrong type of sensor for the application?

Any help that can be offered will be appriciated.

Thanks!

Darkwood · Jan 30, 2016

Welcome to the forum marcusbaxy...

TBH without knowing exactly what you have here it difficult to advise as proxy' sensors do come in many variations - is their a little wiring pic on the side of the cable?

NPN and PNP are both commonly used in my experience but as you are guessing are you sure its either and not just a supply and a volts free nc/no switching?

Also why are you changing the old one - is it obviously damaged or faulty... the issue could be elsewhere and your just re-introducing the problem.

PS here is a link and it has a catalogue in it of their entire sensor range..

http://pdf.directindustry.com/pdf/sick/proximity-sensors/894-383719.html

LeeH · Jan 30, 2016

As you know PNP and NPN are different so the first thing do is find out which it is.

Is you card sink or source?

At a guess you have a sinking card so you need a PNP sensor.

If the fundamentals are correct then I have no idea!

marcusbaxy · Jan 31, 2016

Hi Guys,

Thanks for the replies, I do need to find out more about the sensors. These have been supplied by a 3rd party and I have no information as yet, I can get a part # tomorrow. For now I can run the system manually until I get the info, the client starts production at 06:00 tomorrow morning.

My current idea is to fit 2 x 24vdc relays and supply the coil with the proximity switch signal I have measured and run the 24vdc PLC input through that.

Darkwood · Jan 31, 2016

marcusbaxy said:
Hi Guys,

Thanks for the replies, I do need to find out more about the sensors. These have been supplied by a 3rd party and I have no information as yet, I can get a part # tomorrow. For now I can run the system manually until I get the info, the client starts production at 06:00 tomorrow morning.

My current idea is to fit 2 x 24vdc relays and supply the coil with the proximity switch signal I have measured and run the 24vdc PLC input through that.

Im not sure your sensor is either PNP or NPN as you say its 5core?... standard is 3core for this type of sensor and you can get 4core if you need no/nc options on the switching, its possible it a pnp/npn sensor I havent come across and maybe has intregral delay to avoid false trigger but at the end of the day by the time you get the info figure it all out, its sometimes quicker to just purchase the correct ones and quickly install - the money is saved on geting it running quickly.

If for some reason you need to run a contactor or relay to do the switching then ensure you have a low powered coil or you could blow your sensors.

LeeH · Jan 31, 2016

If it's a 5 core I would say you have a 24v supply and a common n/o n/c set of volt free contacts.

You need to start with the basics and find out what you have.

Let us know.

marcusbaxy · Feb 1, 2016

Okay guys I have some closure.

The proxy turned out to g e a PEC! Dumbass installer. Fitted reflectors, wired up in PNP and connected a 24vdc supply to the grey L/D core to invert the signal. All good and in production now.

Thanks for your support.